I have been thinking. As letterboxing is quite important to the moorland economy, Pubs, Camping etc.
Could it not be discused with the DNPA wether they could let it be known that they support Letterboxing on the moor and they will be willing to prosecute any person or persons caught stealing or tampering with a legitamet moorland past time. This may at least prevent more copy cat theifs.

Any person who without lawful authority permanently removes a Dartmoor Letterbox is committing theft and if caught can be prosecuted by the police. The offence if prosecuted in a magistrates' court currently carries a maximum penalty of a fine of up to £5000 and or 6 months imprisonment.

The DNPA are not a prosecuting authority for the criminal offence such as theft.

I actually meant that they would be willing to suport a prosecution.
I know no one is going to be caught, but it would be nice for the DNPA to puplicly state that they would back a prosecution.
And anybody can bring a prosecution against another person , so actually the DNPA could bring a prosecution, the same way as they would if you decided to park a camper permanently at Meldon.